1. Field of the Invention
The present invention is related to video signal filtering and, more particularly, to interpolative interleaving of video images.
2. Background of the Invention
Television or video images are sequentially scanned in horizontal lines, beginning with the upper left corner of the image and ending at the lower right corner of the image at the end of the scan. Typically, two fields are utilized—an upper field (field 0) and a lower field (field 1). Video can be classified as interlaced or progressive, depending on how the two fields are interleaved into the displayed image.
In some systems, for example TV or other more conventional video display system, field 0 is placed into alternate, even-numbered lines of the image frame in a first pass and field 1 is interleaved into alternate, odd-numbered lines of the image in a second pass. The image is formed from the alternating display of images from the upper and lower fields. This form of interlacing, in television, results in the raster scanning of field 0 into every other video line followed by raster scanning of field 1 into every other video line. Historically, this type of interlaced video relies on the nature of human vision in order to display the video data in a fashion that can be easily transmitted. Thus, transmission of video data in a time-scale acceptable for viewing by the human eye can be accomplished.
In monitors and other digital video systems, progressive scanning can be utilized to display the entire image at once, instead of displaying half the image
In monitors and other digital video systems, progressive scanning can be utilized to display the entire image at once, instead of displaying half the image represented by field 0 pixel data followed closely by displaying the other half of the image represented by field 1 pixel data. Progressive scanning involves displaying the upper field (or field 0) data in even number lines of a video frame (starting with line 0) while display the lower field (or field 1) in the odd number lines of a video frame. In some embodiments, the upper field (field 0) may be displayed first by arranging the field 0 pixel data in the even number lines of the video frame and then the video frame is filled in with the lower field pixel data in the odd-numbered lines of the video image. This type of progressive display results in an image formed from the field 0 pixel data followed by augmentation of the image formed by the field 1 pixel data.
With the increased speed of processing systems that can be utilized to process video data into images, progressive image display resulting from forming a complete image from field 0 and field 1 data before display. The video data, then, is completely compiled in the frame before the image is displayed.
However, with transmission of video data in two fields (i.e., field 0 and field 1), there can be problems with aligning the field 0 data with the field 1 data in order to provide a clear image without artifacts, in either method of progressive display. For example, video noise and miss-timing between the upper and lower field data may be at issue. Where data from field 0 is augmented by data from field 1 in a progressive fashion, flicker or fuzzing of the image may result from misaligned video data. Where data from field 0 and field 1 are compiled together, the resulting image may lose the resolution it might otherwise have if the data from the two fields were better coordinated.
Therefore, there is a need for video display systems that filter interlaced video data in order to provide sharp images in a timely fashion.